Electric motor starters

ABSTRACT

An electric motor starter unit has &#39;&#39;&#39;&#39;start&#39;&#39;&#39;&#39; and &#39;&#39;&#39;&#39;stop&#39;&#39;&#39;&#39; pushbuttons, a solenoid, main contact sets operable by the solenoid, an auxiliary contact set in the solenoid energizing circuit operable by the &#39;&#39;&#39;&#39;start&#39;&#39;&#39;&#39; pushbutton and engageable by the main moving contact carrier to hold the solenoid energized, and an overcurrent trip release device. The insulating moulding is in two parts hinged together, namely a base part on which the auxiliary contact set is mounted and an upper part containing the pushbuttons and the trip release device. A current-sensing unit for the trip release device is a separate unit quickly detachable from the upper insulating moulding part for replacement purposes.

United States Patent Albert W. J. Berry Brighton, England 814,000

Apr. 7, 1969 June I, 1971 Allen West (Brighton) Ltd.

[72] Inventor [2 l] Appl. No. [22] Filed [45] Patented [73] Assignee [54] ELECTRIC MOTOR STARTERS 2,993,967 7/1961 Jelley OTHER REFERENCES Motor Starters, Square D Company Publication, April 19, 1965, Cl 335 Subclass 131 Primary Examiner-Harold Broome Attorney-Holcombe, Wetherill and Brisebois ABSTRACT: An electric motor starter unit has start" and stop" pushbuttons, a solenoid, main contact sets operable by the solenoid, an auxiliary contact set in the solenoid energizing circuit operable by the start pushbutton and engageable by the main moving contact carrier to hold the solenoid energized, and an overcurrent trip release device. The insulating moulding is in two parts hinged together, namely a base part on which the auxiliary contact set is mounted and an upper part containing the pushbuttons and the trip release device. A current-sensing unit for the trip release device is a separate unit quickly detachable from the upper insulating moulding part for replacement purposes.

Ill"

PATENTEB JUN 1 I971 SHEET 1 [IF 9 PATENTEU M 1 ISYI SHEETS [1F 9 L1 L2 L3 PATENTED JUN 1 197i SHEET 5 [IF 9 FIG/Z Fla/l PATENTEDJUN Hem 3582.846

sum 6 OF 9 PATENTED JUN 1 I97! 7 3582.846

SHEET 8 [1F 9 ELECTRIC MOTOR STARTERS The present invention relates to electric motor starter units, that is to say, control units responsive to start" and stop" signals to energize and deenergize motors respectively, and also responsive to undervoltage" and overcurrent to deenergize energized electric motors.

It is an object of the invention to provide an electric motor starter unit which is easy to assemble, requires little if any adjustment prior to use and during use, has no interior wired connections, can readily be adapted for single-phase or polyphase electric motors, can be adapted for manual or remote control and can be adapted for differently rated electric motors.

According to the invention there is provided an electric motor starter unit comprising a solenoid, at least one main contact set operable by the solenoid upon energization thereof, at least one pair of input and output terminals arranged to be interconnected by the or each respective main contact set upon operation thereof by the solenoid, an energizing circuit for the solenoid including start" and hold" contacts selectively operable for initially energizing the solenoid and maintaining the energization of the solenoid, and an overcurrent trip release device responsive to overcurrent to deenergize the solenoid and hence release the or each main contact set, the overcurrent trip release device including at least one current-sensing element in the subunit which is detachable from the remainder of the starter unit by release of a catch for replacement purposes, the or each current-sensing element being electrically connected in series with a respective main contact set through at least one spring contact set.

The invention will be described, by way of example, with reference to the accompanying drawings, wherein:

FIG. 1 is a front elevation of an electric motor starter unit in accordance with the invention;

FIG. 2 is a plan of the starter unit;

FIG. 3 is a side elevation of the starter unit with the casing shown sectioned;

FIG. 4 is a front elevation of a base block member and certain other parts of the starter unit;

FIG. 5 is a plan corresponding to FIG. 4;

FIG. 6 is a side elevation corresponding to FIGS. 4 and 5;

FIG. 7 is a front elevation of an upper moulding block member and certain other parts of the starter unit;

FIG. 8 is a rear elevation of the upper moulding block member and certain other parts of the starter unit;

FIG. 9 is a section on line IX-IX of FIG. 10 to an enlarged scale;

FIG. 10 is a section of line X-X of FIG. 8 to the same scale as FIG. 9;

FIG. 11 is a front elevation of an electromagnet assembly, (including solenoid,) of the starter unit;

FIG. 12 is a side elevation of the electromagnet assembly, with solenoid;

FIG. 13 is a side elevation of an auxiliary contact unit of the starter unit;

FIGS. 14, 15'and 16 are sections of the auxiliary contact unit along the respective lines XIV-XIV, XV-XV and XVI-X- VI; of FIG. 13;

FIGS. 17, 18 and 19 show part of an overcurrent trip release device of the starter unit;

FIG. 20 is a rear elevation of a detachable subunit of the overcurrent trip release device;

FIGS. 21, 22, 23 and 24 are sections along the lines XX- l-XXI, XXII-XXII, XXIII-XXIII, and XXIV-XXIV respectively of the detachable subunit; of FIG. 20;

FIGS. 25, 26 and 27 show one of three current sensing elements in the detachable subunit;

FIG. 28 is a circuit diagram of the starter unit, shown connected up for three-phase;

FIG. 29 is a circuit diagram of a modification for use with single-phase;

FIG. 30 is a circuit diagram of a modification for remote control; and

FIG. 31 is a circuit diagram of a modification with a pilot control switch.

The illustrated electric motor starter unit 10 comprises a support casing 12 formed by a metal case proper l4 and a plastics cover 16, secured together by a screw 18 engaging a pin 19 rivetted to the case 14.

Inside the casing 12 is an assembly 20 comprising a moulded insulating plastics base block member 22 which fits slidably on pin 19 and a second pin 23 also rivetted to the case 14, an upper moulded insulating plastics block member 24 hinged to block 22 by means of two trunnions 26 of block member 24 engaging two sockets 28 in block member 22, three main contact sets 30, 32 and 34 for a three-phase supply (not shown), an auxiliary start and hold contact set 36, an electromagnet assembly 38 including a solenoid 40, an energizing circuit 42 for the solenoid 40, including start and stop" pushbuttons 44 and 46, and an overcurrent trip release device 48.

Three input terminals L1, L2 and L3 are screwed to the base block 22 and are integral with fixed contact blades 50, 52 and 54 forming parts of the respective three main contact sets 30, 32 and 34. The base block 22 is also formed with a cavity 56 for the electromagnet assembly 38 and guides 58 for locating a fixed laminated yoke 60 of the electromagnet assembly 38. A spring blade contact 62 is secured to base block 22 to normally engage a fixed blade contact 64 on upper block 24. Blade contacts 62 and 64 form a normally closed contact set 66 in the energizing circuit 42, operable (to open) by the manual depression of stop pushbutton 46 for deenergizing solenoid 40.

The upper moulded plastics block 24 is formed with a cavity 68 which is complementary to the cavity 56 of block 22. It is also formed with a housing 70 for the pushbuttons 44 and 46 and for part of the overcurrent release device 48. A releasable wire clip 72 is provided for clipping blocks 22 and 24 together. More particularly, the wire clip 72 has two ends entrapped in recesses 74 in block 22, and clips over two lugs 76 integrally formed in block 24.

The three main contact sets 30, 32 and 34 include, besides the above-mentioned fixed contact blades 50, 52 and 54, three movable bridging contacts 80, 82 and 84 mounted in a common moulded plastics carrier block 86 with corresponding compression springs 90, 92 and 94. Contact sets 30, 32 and 34 finally include three further fixed contact blades 100, l02-and 104 which are mounted in the upper block 24.

The auxiliary start" and hold contact set 36 is in the form ofa unit, with fixed contacts 106 and 108 mounted in a transparent moulded plastics housing 110 which is located slidably in guides 112 at the side of base block 22. Movable bridging contacts 114 of contact set 36 are mounted in a transparent moulded plastics carrier block 116. One compres- ;sion spring 118 in housing 110 biases the carrier block 116 upwardly, whereby contact set 36 is normally open, and another compression spring 120 in carrier block 116 serves to bias the bridging contacts 114 and allow for overtravel of block 116 when contact 36 is operated. An upward projection 122 of carrier block 116 is engageable by start pushbutton 44, and a sloping lateral projection 124 of carrier block 116 is engageable by a correspondingly sloping lateral projection 126 of carrier block 86, whereby contact set 36 is held" operated, to maintain energization of solenoid 40, when the main contact sets 30, 32 and 34 are operated.

The electromagnet assembly 38 includes, besides solenoid 40 and fixed yoke 60, a nylon block 127 which is pinned to yoke 60 and secured in the guides 58 of base block 22, a laminated armature 128 and a steel frame 129. The fixed yoke 60 is generally E-shaped, with a central core 130 and two side limbs 132 and 134, side limbs 132 and 134 being provided with copper shading rings 136 and 138. Armature 128 is also generally E-shaped with a central core 140 and two side limbs 142 and 144. The steel frame 129 is generally U-shaped, with the ends of its two side limbs 146 and 148 rivetted to carrier block 86 at 150 and 152 and its center limb 154 pivoted to armature 126 by means of a steel pin 156. Finally, assembly 38 may include a compression spring I58 located on core 140 of armature 126 to bear against solenoid 40. Alternatively gravity alone, (without spring 158,) may be relied upon to release the armature 128. Solenoid 40 is located by a projection 159 (FIG. 8) of moulding 70. Solenoid 40 includes two metal contacts 160 and 162 which make sliding contact with two metal contacts 164 and 166 on upper block 24.

The energizing circuit 42 for solenoid 40 for three-phase operation is connected to input terminals L1 and L3 and comprises the auxiliary start and hold" contact set 36, the normally closed contact set 66 and a bistable contact set 168 of the overcurrent release device 48, contact set 168 being normally closed. A first copper strip 170 connects terminal L1 to terminal 172 of contact set 36. A second copper strip 174 connects terminal 176 of contact set 36 to a terminal 178 which is integral with the spring blade contact 62 of contact set 66. The fixed blade contact 64 of contact set 66 is connected to a moving blade contact 180 of the contact set 168 of the overcurrent release device 48. A fixed contact 182 of contact set 168 is connected by a brass strip 184 integral with the above-mentioned contact 164. The solenoid contacts 160 and 162 engage contacts 164 and 166, as mentioned above. Contact 166 is integral with a brass strip 186 which has an annular portion 188 on the adjacent one of the two trunnions 26 in face-toface contact with an annular portion 190 of another brass strip 192, integral with a terminal 194 on the opposite side of block 22 from contact set 36. Finally, an insulated wire conductor 196, (not shown in FIG. 4,) the only wire conductor in the entire starter unit 10, connects terminal 194 to terminal L3.

In modification (not shown) for possible use with threephase star or Y supply, wire conductor 196 is removed and the neutral of the supply is connected to terminal 194.

In another modification shown in FIG. 29, for use with a single-phase supply, (taken to terminals L1 and L3,) output terminal A, (referred to hereinafter,) corresponding to input terminal L1, is connected by a conductive strip or insulated wire (not shown) to terminal L2, and the single-phase electric motor, (also not shown), is connected to output terminals B and C, (also referred to hereinafter,) corresponding respectively to input terminals L2 and L3.

In another modification, (not shown,) a separate supply may be connected to terminals 172 and 194, with strip 170 and wire 196 removed. This separate supply may be DC instead of AC if desired, with a suitable solenoid 40.

In yet another modification shown in FIG. 30, remote control" may be achieved by way of a remote normally open start contact set 198, with pushbutton 200, in series with a remote normally closed stop contact set 202, with pushbutton 204, connected to terminals 172 and 178, and with a connection 206 between the junction 208 of contact sets 198 and 202 and terminal 176, the strip 174 being removed.

In a fifth modification shown in FIG. 31, a pilot control switch PS may be connected across terminals 172 and 178, with strip 174 removed.

The pushbuttons 44 and 46 are respectively provided with coiled compression return springs 45 and 47.

The overcurrent trip release device 48 is in two parts 210 and 212.

Part 210 is in the form of a detachable subunit formed by a moulded insulating plastics support or housing 214 containing three electrical resistance heater current-sensing" elements 216, 218 and 220 corresponding to the three phases of the supply and arranged to be respectively electrically connected between the three input terminals L1, L2 and L3 on the one hand and the above-mentioned three output terminals A, B and C on the other hand. Each element 216, 218, 220 consists of one or more heater wires 222 wound over a glass-fiber sleeve 224 on a bimetal strip 226. One end of the or each wire 222 is resistancewelded to the respective bimetal strip 226, which is resistancewelded at 227 to a respective one of three metal supports 228. The other end of the or each wire 222 is resistance-welded to a respective one of three metal connector elements 229.

The high expansion" side of each bimetal strip 226 faces away" from the part 212 of device 48.

The three output terminals A, B and C are mounted directly on three respective spring blade contacts 230, 232 and 234 on block 24, arranged to engage the three respective supports 229 to make electrical contact therewith. Three further spring blade contacts 236, 238 and 240 on block 24 are integral with contact blades 100, 102 and 104, (forming parts of the three main contact sets 30, 32 and 34,) and are arranged to engage and thus make electrical contact with the three respective connector elements 228. Thus the three elements 216, 218 and 220 are electrically connected between terminals L1, L2 and L3 on the one hand and terminals A, B and C on the other hand, to carry the three-phase currents of the electric motor load (not shown) connected to terminals A, B and C.

Finally, unit 210 includes a trip bar" member 242 slidable arranged in housing 214, laterally with respect to and engageable by each of the bimetal strips 226. The bimetal strips 226 are arranged for overheating of any one of them, due to excess current or overcurrent, to displace the trip bar member 242 longitudinally of itself (and sideways of strips 226) to operate a trip switch button 244 in part 212 of the overcurrent release device 48 and thereby changeover, (that is, open,) contact set 168 to deenergize solenoid 40 and thereby release, that is, open) the main contact sets 30, 32 and 34.

The unit 210 is normally attached to block 24 by means of two hooks 246, integrally moulded in housing 214, engaging two corresponding recesses 248 in block 24, and a springloaded quick release" catch 250 on block 24 engaging a recess 252 on the opposite side of housing 214.

By being detachable in this way, unit 210 can readily be exchanged for another such unit, (not shown,) with differently rated electrical resistance heater elements, (corresponding to elements 216, 218 and 220,) for different current loads.

The part 212 of the overcurrent release device 48 is housed in block 24. Firstly, it comprises the trip switch button 244 referred to above, operable by the trip bar member 242 (of unit 210). Part 212 further comprises a bimetal strip 246 engageable by button 244 and welded to a spring steel strip 248 to form an ambient temperature-compensating lever 250. The high expansion side of strip 246 faces button 244.

Thus, the bimetal strip 246 bends away from button 244 when the ambient temperature rises, thus compensating for a corresponding bending movement of bimetal strips 226 in unit 210 towards button 244 due to the rise in ambient temperature.

Lever 250 is efi'ectively pivoted on an adjustable pivot pin 252, in a manner to be described thereinafter, so that operation of button 244 by member 242, (moving button 242 to the right as seen in FIG. 9,) pivots lever 250 clockwise as seen in FIG. 9 around pivot pin 252. A trip switch lever 254 is pivoted on a pivot pin 256 to be rotated anticlockwise (or counterclockwise) by lever 250 as seen in FIG. 9, and serves to open contact set 168.

The movable blade contact of contact set 168 is an integral part of a flexible element 258. Element 258 also comprises an integral biasing limb 268. A toggle spring 270 is connected between blade contact 180 on the one hand limb 268 on the other hand, to bias them apart. The element 258 is rivetted to a mounting plate 272 to which the pivot pin 256 is also rivetted. Normally, the contact set 168 closed, blade 180 is biased to the left of limb 268 as seen in FIG. 9 by toggle spring 270, urging a contact point 266 of blade 180 against contact 182.

An am 274 of the trip switch lever 254 is engageable with the biasing limb 268 of element 258, so that the anticlockwise pivoting of lever 254 produced by operation of button 244 by member 242 causes limb 268 to be pushed to the left as seen in FIG. 9, until an overcenter" position is reached, whereupon the toggle spring 270 snaps blade contact 180 to the right as seen in FIG. 9, opening contact set 168.

Reclosure of contact set 168 can be arranged to occur auto matically, once bar member 242 returns to its normal position. Alternatively, reclosure can be arranged to occur only upon operation of stop" button 46.

To effect reclosure of contact set 168, there is provided a lever 276 pivoted at 278 inside of a transparent cover plate 280. An adjustment lever 282 is pivoted also at 278 externally of cover plate 280, and is secured in the position shown by a screw 284. A part 286 of lever 282 projects internally of cover plate 280, adjacent screw 284, and a torsion spring 288 acts between the projection 286 and a projection 290 on lever 276 to bias lever 276 clockwise as seen in FIGS. 9 and 17.

Stop pushbutton 46 is provided with an enlarged portion 292 which forms a cam to engage the projection 290 on lever 276 and cam lever 276 anticlockwise as seen in FIG. 9 when button 46 is depressed. When lever 276 is cammed anticlockwise in this way, a projection 294 (on the opposite end of lever 276 from projection 290) moves blade contact 180 to the left as seen FIG. 9, returning blade 180 to an overcenter" position whereat the toggle spring 270 snaps 268 to the right of blade 180 and snaps blade 180 into engagement with contact 182.

For operation of stop" pushbutton 46 to be necessary to reset contact set 168, lever 282 has to be in the position shown, marked H" for hand."

If lever 282 is pivoted anticlockwise (about pivot 278) to the A" position, (meaning auto) shown, then resetting of contact 168 is automatic once trip bar member 242 is allowed to retract into housing 214 upon cooling down of all the heater elements 216, 218 and 220, or whichever of them became overheated. This automatic resetting of contact set 168 takes place because, with lever 282 in the A position, the projection 294 on lever 282 limits the rightward movement of blade 180 when operated by the trip bar 242.

With reference to the above-mentioned pivoting of lever 250 on adjustable pivot pin 252, the pivot pin is screwthreaded and screw-headed, and is adjustably screw-threaded into an adjustable calibration dial 296, itself rotatably mounted on block 24. A narrow stem 298 of pivot pin 252 locates in apertures in the bimetal strip 246 and spring steel strip 248, and a shoulder 300 on pivot pin 252 bears against the spring steel strip 248, so that pivot pin 252 may be adjustably screwed into or out of dial 296, the effective pivot point of lever 250 is correspondingly adjusted. It is the pivot pin 252 which is adjusted, for a given setting of dial 296, (as to be described) for a predetermined level of current overload to operate or trip contact set 168.

The calibration dial 296 itself is screw-threadedly mounted in an insert 298 in block 24, so that rotational adjustment of dial 296 itself moves pivot pin 252 into or out of block 24. This enables a given unit 210 to be used for tripping contact set 168 at any desired level of overcurrent within a certain range. The dial 296 is suitably calibrated.

lclaim:

I. An electric motor starter unit comprising a solenoid, a main contact set operable by the solenoid upon energization thereof, a pair of input and output terminals arranged to be interconnected by the main contact set upon operation thereof by the solenoid, an energizing circuit for the solenoid including start" and hold contacts in said circuit selectively operable for initially energizing the solenoid and maintaining the energization of the solenoid, and an overcurrent trip release device, including a current sensing element, responsive to overcurrent to deenergize the main contact set, said sensing element being located in a subunit and comprising catch means by which said subunit is connected to the remainder of the device and starter unit and readily detachable therefrom for replacement purposes, together with means including a spring contact set for automatically electrically connecting the sensing element in series with the main contact set during attachment of the subunit to the remainder of the device.

2. A starter unit as claimed in claim 1, comprising a housing for said solenoid consisting of a first insulating member hinged to a second insulating member, said second insulating member being provided with means for securing it to a support, and a readily releasable catch for retaining the first and second members in a closed condition.

3. A starter unit as claimed in claim 2, wherein said overcurrent trip release device comprises a normally closed contact set in said energizing circuit, said overcurrent trip release device is carried by said first insulating member, and part of said energizing circuit is mounted on said second insulating member and is electrically connected to said contact set of said overcurrent trip release device by means of two conductive metal strips mounted respectively on said first and second insulating members and in face-to-face electrical contact at said hinge.

4. A starter unit as claimed in claim 2, comprising a plurality of pairs of input and output terminals, a contact set for each pair of terminals, and a current-sensing element for each pair of terminals, wherein said subunit of said overcurrent trip release device is mounted detachably on said first insulating member, one terminal of each pair is mounted on said first insulating member, the other terminal of each pair is mounted on said second insulating member, each main contact set comprises two fixed contacts mounted one on said first insulating member and the other on said second insulating member and a movable bridging contact operable by the solenoid, at least one spring blade contact mounted on said first insulating member connects with respective terminal mounted on said first insulating member to its respective current-sensing element, and at least one further spring blade contact mounted on said first insulating member connects each current-sensing element to its respective fixed contact mounted on said first insulating member.

5. A started unit as claimed in claim 1, wherein there are three main contact sets operable by the solenoid upon energization thereof, and three pairs of input and output terminals.

6. A starter unit as claimed in claim 1, wherein said start and hold" contacts are formed by an auxiliary contact unit, a carrier member carrying a movable contact of the main contact set being formed with a cam which is engageable with said auxiliary contact unit upon operation of the main contact set to hold said auxiliary contact unit operated.

7. A starter unit as claimed in claim 6, comprising a start pushbutton in the starter unit for engaging said auxiliary contact unit.

8. A starter unit as claimed in claim 3, wherein said start and hold" contacts are mounted on said second insulating member. 

1. An electric motor starter unit comprising a solenoid, a main contact set operable by the solenoid upon energization thereof, a pair of input and output terminals arranged to be interconnected by the main contact set upon operation thereof by the solenoid, an energizing circuit for the solenoid including ''''start'''' and ''''hold'''' contacts in said circuit selectively operable for initially energizing the solenoid and maintaining the energization of the solenoid, and an overcurrent trip release device, including a current sensing element, responsive to overcurrent to deenergize the main contact set, said sensing element being located in a subunit and comprising catch means by which said subunit is connected to the remainder of the device and starter unit and readily detachable therefrom for replacement purposes, together with means including a spring contact set for automatically electrically connecting the sensing element in series with the main contact set during attachment of the subunit to the remainder of the device.
 2. A starter unit as claimed in claim 1, comprising a housing for said solenoid consisting of a first insulating member hinged to a second insulating member, said second insulating member being provided with means for securing it to a support, and a readily releasable catch for retaining the first and second members in a closed condition.
 3. A starter unit as claimed in claim 2, wherein said overcurrent trip release device comprises a normally closed contact set in said energizing circuit, said overcurrent trip release device is carried by said first insulating member, and part of said energizing circuit is mounted on said second insulating member and is electrically connected to said contact set of said overcurrent trip release device by means of two conductive metal strips mounted respectively on said first and second insulating members and in face-to-face electrical contact at said hinge.
 4. A starter unit as claimed in claim 2, comprising a plurality of pairs of input and output terminals, a contact set for each pair of terminals, and a current-sensing element for each pair of terminals, wherein said subunit of said overcurrent trip release device is mounted detachably on said first insulating member, one terminal of each pair is mounted on said first insulating member, the other terminal of each pair is mounted on said second insulating member, each main contact set comprises two fixed contacts mounted one on said first insulating member and the other on said second insulating member and a movable bridging contact operable by the solenoid, at least one spring blade contact mounted on said first insulating member connects with respective terminal mounted on said first insulating member to its respective current-sensing element, and at least one further spring blade contact mounted on said first insulating member connects each current-sensing element to its respective fixed contact mounted on said first insulating member.
 5. A started unit as claimed in claim 1, wherein there are three main contact sets operable by the solenoid upon energization thereof, and three pairs of input and output terminals.
 6. A starter unit as claimed in claim 1, wherein said ''''start'''' and ''''hold'''' contacts are formed by an auxiliary contact unit, a carrier member carrying a movable contact of the main contact set being formed with a cam which is engageable with said auxiliary contact unit upon operation of the main contact set to hold said auxiliary contact unit operated.
 7. A starter unit as claimed in claim 6, comprising a ''''start'''' pushbutton in the starter unit for engaging said auxiliary contact unit.
 8. A starter unit as claimed in claim 3, wherein said ''''start'''' and ''''hold'''' contacts are mounted on said second insulating member. 